Rough Idle - Check Engine Light

If you haven't given it a tune-up recently, give it a tune-up. 02 sensors are part of a tune-up. As far as cylinder number 2, check fuel--spark and compression on that cylinder.

Just to add, can you give us the actual code #? What is the engine litre size? For cylinder #2 misfire, it should be p0302. Our database doesn't even list that code?

I actually didn't get the code myself. I had a buddy bring it to a car part place and they read the code.

Like I said I just bought it so I have no clue if and when if it ever had a tune up.

If a tune up is step one what should that all entail?

Plugs, and what else? Is this something a layperson can do or does it need to be done by a shop with the diagnostics?

Spark plugs--spark plug wires--dis. cap and rotor where applicable. Check or change filters, air and fuel. With the fuel filter make sure no pressure on the system before taking any fuel lines loose. Check all fluids. Like I said 02 sensors are part of a tune-up. Use a gage and check fuel pressure. I'm sure I'm leaving something out.

Make sure all the lites work front and rear/ turn signals--brake lites--tail lamps--tag lite. Make sure the horn works. Check the air in the tires.

What's engine litre size?

do these vehicle even have a rotor? I think they are all electronic ignition.

why replace all o2 sensors? or is there only one.. not sure..

I asked about engine litre size. The v8 shows coil near plug, no distributor. My info shows 4 oxygen sensors. I'd replace the front two for a start.

shouldn't I just replace the one that is bad??

With a tune-up, I'd replace the front two. It's your vehicle, do what ever you want. I doubt if replacing all four would hurt, anything.

If money is an issue, replace only one, that's up to you.

For now I did just the one throwing the error code.

I pulled and replaced all spark plugs with OEM plugs and replaced the wires.

I also changed the air filter and the fuel filter.

After I did all of this I drove it for about 5-6 miles. Check Engine light still on but only solid not blinking.

I just drove it again and within the first few blocks the check engine light went off and stayed off for that drive.

I have an reader coming tomorrow so I will scan it again for codes.

The plugs were really really bad. some didn't even have tips and the gaps were huge.

Sounds like your headed in the right direction. Keep us posted.

Too good to be true... the suburban is now throwing the following codes:

Most recent read:
p 0171 system too lean bank 1

p0 300 random multiple cylinder misfire detected

prior read:
p 0131 02 sense or circuit low voltage bank 1 sensor 1

p 0171 system too lean bank 1

p 1153 manufacturer control

prior read:
p 0171 system too lean bank 1


What is the solution to these codes??

Have you changed the 02 sensor? Also, check the 02 sensor wiring circuit.

I changed bank 2

not sure about how to check the circuit.

Just to add, the most common causes for po171 are, miscalibrated maf sensor--- exhaust or intake vacuum leaks---low fuel pressure/volume.

How does one correct a miscalibrated MAF sensor?

Not sure how I find the exhaust/vacuum leak

Fuel pressure, not sure how that is checked either but I did change the fuel filter.

With the engine idling, you could tap on the maf sensor, see if any effect on the idle. As far as exhaust leak, get under the vehicle and check it out.
As far as intake, you could spray some wd40 or something around the gasket areas, if the rpms take off, you found a leak.
As far as fuel pressure, use a gage and check fuel pressure. Some of the national brand autostores will loan out a fuel pressure gage. You may have to put up a deposit, but, you get it back when you bring the tool back.

Just wanted to add, anytime you use a flammable spray of any king, you have to be careful about starting a fire or anything. Safety is your responsibility.

where do I find the maf sensor? I am not familar with it?

is it something that can be easily replaced to solve these error codes?

Ok. I am going to look at the Mass Air Flow now that I know what it is.... had to look it up.

I am going spray some cleaner in it... but not sure that will solve the issue.

Don't these just need to be replaced over time???

Can you visually look at the MAF and know it is bad or dirty, etc?

My info says to not spray anything on it. The code doesn't tell you what to replace just that the system thinks there is problem on that circuit somewhere.

Forget the codes for a minute. Are there any driveability issues, still, after what you've done? If no driveability issues and no check engine lite, sounds like your good to go.

it keeps throwing similar codes each time I drive it.

do you think these issues could be tied to a dirty/faulty EGR value?

I've not looked at it but I did get these codes after cleaning the MAF.

P0171. Too lean bank 1

P0300 random\multiple cylinder misfire

P0404 exhaust gas recirculation control circuit range / performance

I don't think I have mentioned this but the exhaust spews out black carbon when you throttle it. I.e. all over side of garage wall.

The egr should only be an issue at idle. I asked if there were driveability issues??? Is the check engine on??? As far as the vehicle running rich, have you checked fuel pressure and fuel pressure leak down?

At the moment, I don't care about the codes.

If ignore the codes the only issues is at idle.

driving down the road it seems to drive just fine, other than the check engine light is one.

The only other thing is at idle it seems like it is rough and at time might die but never has.

Only other thing is the black crap that comes out the tail pipe

I don't know how to do the fuel pressure checks.

The egr could have an effect at idle, so could a vacuum leak. You should have a Schrader valve on your fuel rail under the hood. The fuel pressure gage screws onto the Schrader valve.

could the egr cause the prior codes?

It's possible.